आज भिडदै छ 'बराह' ।

नेपाली रोबोट 'बराह्'ले आज भियतनामको हनोईमा १८ देशका १९ टिमसँग दर्‍हो प्रतिष्पर्धा गर्ने रोबोटिक्स क्लबले जनाएको छ ।जापान, चिन, कोरीया जस्ता बिकसित् देशको रोबोटसँग नेपालले कडा चुनौतिको सामना गर्नुपर्ने यो खेलमा समुह छनौटको बिवरण भने प्राप्त भएको छैन ।

BARAHA IN ABU ROBOCON 2007, VIETNAM

There are three automatic machines, the basic features of each of these robots are briefly explained below.

First Automatic Machine (Largest automatic):
Sensors used:
LDR sensors: These are Light Dependent Resistors which changes its resistance as the intensity of light incident on it is varied. We have used LDR’s for tracking the white guide lines of the gamefield as these sensors give different response for white lines from the remaining part of the game field. Since these sensors are completely dependent of light intensity, it should be properly shielded from ambient light.
ii) IR sensor: The infra red sensor is used to detect the object. The machine gets to know from what height to release the pearl on island with the help of this sensor which sends signal to the controller when object is detected in front of it.
Limit Switches: Simple limit switches are used to know the physical positional limit of different parts. For example the slider has the lower and upper limit and motor must be stopped when slider reaches this limit. The limit switches cuts the electric signal when it is pressed physically.
Motor Driver:
The motors are driven with the H-bridge made up of n-channel mosfet. We designed the H-bridge circuit but it took much time to refine it and make it reliable with lots of protection added to the simple H-bridge circuit. It was a great to see the stepwise improvement of the circuit as we experimented and analyzed it for almost a week. We were exhilarated when it finally worked very well.
Mechanical features:
The machine consists of a slider that allows the vertical movement of the grip so that the machine can pick the pearl from the floor and then put it on the island. The sliding mechanism uses rack and pinion arrangement. The grip uses pulley to grip and release the pearl. Similarly, there is stack rod on the machine that is used to stack the picked pearl. Stack can rotate in horizontal plane with a range of about 120 degree.

SECOND AUTOMATIC MACHINE(medium sized robot):
Sensors used:
As the first robot it uses ldr to track the lines.
Optical encoder: The optical encoders are attached to the small disc and the disc will rotate as the machine moves. The optical encoder gives pulses at the rate proportional to the speed of the machine. In this way feedback is taken from the encoder and is used to determine the position of the robot, The same feedback approach is taken along with our control algorithm to make robot move in a straight path when required.
IR sensors and limit switches: Same use as that in first automatic machine.
Motor Driver:
As with previous machine, our custom made H-bridge driver is used. Since the feedback system is used for speed control the bridge circuit is enhanced with PWM (Pulse Width Modulation) input, so the speed of motor is proportional to the duty cycle of pwm input.
Mechanical feature:
It is pretty similar to the first automatic machine. The stack rod is not present in this machine. Apart from that all other mechanism are same.

THIRD AUTOMATIC MACHINE(small sized robot)
This is a very simple machine with very limited task of defense. We had thought of enhancing its feature to use it in offence to. However the time limitation prevented us from modifying it. .

MANUAL MACHINE:
The manual machine consists of simple electronics. It simply consists of driver circuit with relays and limit switches. It has relatively complex mechanisms compared to automatic machines.
The sliding mechanism is similar as that of automatic machines. Further it contains slider that can slide horizontally. The gripping mechanism is bit different from that of automatic machines to allow greater tolerance in gripping the pearl. It has two grips that are controlled individually. We had suspension system to absorb the shock. However the inherent complexity of this system in controlling the machine and very limited time to modify it compelled us to remove the system.